The present invention relates broadly to packings, seals, pistons, and like components for reciprocating or otherwise movable machine parts such as may be found in hydraulic or pneumatic cylinders or other actuators, and more particularly to a retainer for such components which may be used to retain such components in or on a machine part without the need to machine a full cavity or gland in the part for receiving the component.
Fluid seals, also known as packing rings, for machine part joints are well-known in the art. A typical application therefor involves the provision of a fluid seal intermediate relatively movable or reciprocating surfaces such as the outer surface of the rod of a hydraulic or pneumatic cylinder, or other fluid actuator, which reciprocates axially relative to an internal bore or other inner surface of a stationary, surrounding housing. Such seals, known in the vernacular as rod seals, conventionally are configured in a free state as a generally annular element which is molded or otherwise formed of an elastomeric or other resilient material such as a synthetic, natural, or co-polymer rubber, or a polymeric material such as a silicone, fluoropolymer, or, preferably, a polyurethane or fluoropolymer. Typically, the rod seal element is seated within an annular sealing gland or cavity which is provided within one of the surfaces, such as an internal bore of the cylinder housing, with the opening of the gland oriented as facing the other surface such as the outer surface of reciprocating rod. Within the gland, the seal is interposed between the rod, which is received coaxially through the seal for reciprocation within the cylinder bore, and a circumferential, peripheral side wall of the gland. As the piston rod reciprocates along a longitudinal axis within the bore, the seal functions to engage the reciprocating surface of the piston and the side wall of the gland to provide, respectively, a dynamic and static seal therebetween. In this regard, as installed under stress within the gland the seal presents in an energized or deformed state low and high pressure radial surfaces each disposed adjacent a corresponding side of the fluid pressure system, and inner and outer axial surfaces each defining one or more contact surfaces with a corresponding, opposing surface of the rod and gland.
It has been observed, however, that the machining of a full gland, i.e., having both a forward and rearward end wall, in the rod, housing, or other machine part sometimes presents difficulties. For example, in the case of small piston and rod sizes, tooling limitations and space constraints complicate the machine of a full gland. Moreover, and depending upon the relative geometry of the respective machine parts, the installation of a seal or the like within a full gland is itself sometimes problematic.
The demands on fluid power equipment, such as hydraulic cylinders and other actuators, occasioned by higher operating pressures, harsher service environments, closer tolerances, smaller sizes, and other factors have continued to increased. It therefore will be appreciated that further improvements in seals and sealing systems therefor would be well-received by the industry.
The present invention is directed to improvements in the mounting of seals, packing, pistons, and like components within machine assemblies having, for example, a reciprocating shaft such as a piston rod or ram of a hydraulic or pneumatic cylinder or other actuator. The improvement includes the provision of a generally annular, collet-like retainer which is receivable within a gland defined between a first and a concentric second machine part of the machine assembly.
The assemblies of the type herein involved may be characterized generally as including a first machine part having a generally annular surface which extends along a central longitudinal axis, and a second machine part having a generally cylindrical surface disposed in concentric opposition to the annular surface of the first machine part. One or both of the machine parts may be reciprocatingly movable relative to the other machine part in a forward and a rearward direction along the central longitudinal axis.
In accordance with the precepts of the present invention, a first one of the surfaces of the first or second machine part is provided as having a gland defined therein. The gland is formed as having a forward end wall and a first peripheral wall. The first peripheral wall is spaced-apart a first radial distance from the opposing second one of the surfaces of the first or second machine parts, and extends intermediate the forward end wall and an open rearward end. The gland further has a second peripheral wall which is formed contiguously with the first peripheral wall intermediate the forward end wall and the open rearward end. The second peripheral wall is spaced-apart a second radial distance greater than the first radial distance from the opposing second one of the surfaces of the first or second machine part, and terminates at a rearward end wall.
The retainer includes a generally annular body configured to be receivable coaxially intermediate the first and second machine parts. The body extends along the longitudinal axis from a forward end portion receivable within the gland to a rearward end portion configured as defining a plurality of cantilevered segments, each of the segments extending from a proximal end to a distal end and having a camming surface. The segments are resiliently yieldable responsive to the bearing of the camming surface on the first peripheral wall of the gland to allow the retainer forward end portion to be advanced coaxially along the gland first peripheral wall and into disposition within the gland intermediate the second peripheral wall and the forward end wall thereof. The distal end of the segments is interferingly engageable with the rearward end wall of the gland delimiting rearward movement of the retainer forward end portion out disposition within the gland.
In a first illustrative embodiment particularly adapted, for example, for the retention of rod seals and the like, the gland is defined within the annular surface of the first machine part with the first peripheral wall being sized as having a given first diametric extent. The camming surface of the retainer body segments extends radially outwardly with respect to the longitudinal axis to define a second diametric extent of the segments which is greater than the first diametric extent of the gland first peripheral wall. However, in order to allow the retainer body forward end portion to be advanced along the gland first peripheral wall, the retainer segments are made to be collapsible radially inwardly responsive to the bearing of the camming surface on the gland first peripheral wall.
In a second illustrative embodiment particularly adapted, for example, for the retention of piston seals and the like, the gland is defined within the cylindrical surface of the second machine part with the first peripheral wall being sized as having a given first diametric extent. The camming surface of the retainer body segments extends radially inwardly with respect to the longitudinal axis to define a second diametric extent of the segments which is less than the first diametric extent of the gland first peripheral wall. However, in order to allow the retainer body forward end portion to be advanced along the gland first peripheral wall, the retainer segments are made to be expandable radially outwardly responsive to the bearing of the camming surface on the gland first peripheral wall.
Particularly in either of the first and second embodiments, a unidirectional or bidirectional, generally annular fluid seal member may be retained by the retainer within the gland. In this regard, the forward end portion of the retainer body is provided to terminate at a forward radial end surface, with the rearward end portion of the retainer body terminating at a rearward radial end surface. The fluid seal member is mounted separately or integrally with the retainer forward end portion within the gland intermediate the forward end wall thereof and the forward radial surface of the retainer body. The rearward radial end surface of the retainer body is abuttingly engageable with the rearward end wall of the rearward gland to retain the seal member intermediate the gland forward end wall and the forward radial end surface of the retainer body. Optionally, the seal member may be bonded to the forward radial end surface of the retainer, with the seal member being formed in such arrangement of an elastomeric material, and the retainer being formed of resilient plastic material.
Alternatively, and particularly in the second mentioned embodiment, the retainer may be configured a having a radially-outwardly extending forward radial surface and a radially-outwardly extending rearward radial surface spaced-apart from the forward radial surface along the longitudinal axis to define a circumferentially-extending portion therebetween. In such a configuration, the retainer may function as a piston head in that the circumferentially-extending portion may be made responsive to a fluid pressure acting on one of the forward or the rearward radial surface to move the second machine part in a corresponding forward or rearward direction.
The present invention, accordingly, comprises the apparatus and method possessing the construction, combination of elements, and arrangement of parts and steps which are exemplified in the detailed disclosure to follow. Advantages of the present invention include the provision of a retention system for the installation of components in or on one of a pair of reciprocating machine parts which is adaptable to a variety of part sizes and geometries. Additional advantages include a method of retaining seals, pistons, and other components between reciprocating machine parts which facilitates the installation of the component while obviating the need machine a full cavity or gland in the parts. These and other advantages will be readily apparent to those skilled in the art based upon the disclosure contained herein.